In a traditional plug and socket outlet system, the electrical contacts are fixed and stationary within both the plug and socket outlet side, respectively. Therefore, the relative separation speed between the plug contacts and the outlet contacts is determined only by the manual removal speed of the plug. In addition, due to the uncertainty of the personnel who operates the device, the removal speed changes over a large range and essentially is not regulated.
One example application of such contacts is a direct current (DC) plug and socket outlet device. The new low voltage direct current (LVDC) socket outlet and plug devices are required by DC distribution applications such as DC datacenters, DC commercial buildings and residential houses, in order to distribute the power to the end equipment, appliances and electronics. Unlike the AC socket outlet and plug, there is no natural zero crossing instant for either voltage or current in the DC distribution system. When the plug is disconnected from the socket outlet with DC load current, significant arcing will be generated. While in the AC system, the arcing can be quenched automatically at the voltage/current zero crossing quickly. Without a proper extinction approach, DC arc generates a large amount of energy and heat that can be more than one kilo-Joule, and can last up to a few seconds if the plug is separated too slowly. Therefore, DC arcing can cause a fire hazard, injure personnel, damage the plug and socket outlet device, and greatly reduce the operating cycles of the outlet device with poor reliability. As a result, DC arcing extinction approaches must be considered for the DC plug and socket outlet device to guarantee safe and reliable connection and disconnection operations.
Newer DC socket outlets include an electromagnetic arc extinction unit to quench the arc when the plug is separated from the socket outlet. The magnetic field applied by an electro-magnet stretches the arc with Lorenz force and the arcing cannot sustain and is therefore extinguished quickly. However, even with the electro-magnet, some minimal separation speed between the plug and outlet side contacts is still required in order to keep the arcing energy in low level for both human safety and the life cycles of the device.
Thus, there is a need to provide sliding contact assembly that is constructed and arranged to ensure a certain separation speed between the plug and outlet side contacts.